Estudo da síntese, caracterização e desempenho de fotocatalisadores de Nb2O5

Abstract

The pollution of aquatic environments has been a constant concern in recent decades. In view of this, industries whose effluents have greater potential polluter, or by its large volume, or by the potential toxicity of the substances eliminated, should invest in most effective methods of wastewater treatment. The Advanced Oxidation Processes (AOPs) has emerged as an alternative to rapid and effective degradation even for compounds whose mineralization by conventional chemical or biological agents is hampered. The heterogeneous photocatalysis is one of the POAs that has wide applicability. Studies revolve around the substrates that can be degraded from this technique, and also around what photocatalysts can be used more efficiently. Of these, the one that stands out is the titanium dioxide (TiO2), due to its high photocatalytic activity, low toxicity and high stability. The niobium pentoxide (Nb2O5) also deserves attention, because posseses the structural characteristics and bandgap similar to TiO2 and also due its abundance in Brazil, which greatly reduces its cost. In this work, were performed the synthesis of Nb2O5 from calcination of niobic acid (Nb2O5.nH2O) at three different temperatures (500, 700 and 900 ° C). The compounds obtained were characterized by adsorption/desorption of N2 and scanning electron spectroscopy in order to determine its structural characteristics. Tests of photocatalytic degradation of Reactive Black 5 dye at a concentration of 50 mg.L-1, pH 10 were also conducted, and the variables were the type of the photocatalyst prepared and its mass. The results showed a structure with low surface area and pore volume, and low photoactive. It was found from the optimization that the best condition was 652,2 mg.L-1 of Nb2O5 calcined at 500 °C, from which was obtained a 19% reduction in total field. Besides the photocatalytic tests, comparative testing of performance between TiO2 and Nb2O5, duration of response and representativeness of photolysis and adsorption in the final degradation helped the results to become more consistent.